feat: add support for external cli in bg agents

[antoniomdk]

Summary

• Add extensible external CLI framework for background agent execution
• Implement Cursor as the first provider, allowing users to leverage existing Cursor subscriptions
• Enable opt-in configuration to route background tasks through external CLI tools instead of OpenCode's native agent system

Changes

New Feature: External CLI Backend

• Users can now configure external CLI tools to handle background agent tasks
• Cursor provider implemented with full support for model selection and workspace configuration
• Extensible provider interface allows future CLI integrations (e.g., aider, codex)

Configuration

{
  external_cli: {
    enabled: true,
    provider: cursor,
    models: {
      explore: gpt-5.1-codex-mini,
      librarian: gpt-5.2
    },
    default_model: gpt-5.1-codex,
    timeout: 300000
  }
}

New Files

• src/features/external-cli/ - External CLI framework
  • types.ts - Provider interface and config types
  • executor.ts - Provider management and execution
  • providers/cursor.ts - Cursor CLI provider implementation
  • providers/index.ts - Provider factory

Modified Files

• src/config/schema.ts - Added ExternalCliConfigSchema with provider selection
• src/features/background-agent/manager.ts - Route to external CLI when enabled
• src/features/background-agent/types.ts - Added external-cli backend type
• src/tools/background-task/tools.ts - Display external-cli backend in task status
• src/index.ts - Wire up external CLI config to BackgroundManager
• README.md - Documentation for external CLI configuration

Adding New Providers

The system is designed for extensibility:

1. Add provider name to ExternalCliProviderSchema in schema.ts
2. Create provider class implementing ExternalCliProviderInterface
3. Register in providers/index.ts

##Testing

• Added unit tests for provider factory and type contracts
• All 630 tests passing

---

Summary by cubic

Adds an external CLI backend for background agents with a Cursor provider, letting users run tasks through Cursor instead of OpenCode. Opt-in via config; tasks and results clearly label the backend.

• New Features

  • External CLI framework with an extensible provider interface.
  • Cursor provider with model selection, workspace, and timeout; executes via cursor-agent with JSON output.
  • BackgroundManager routes to external CLI when enabled; tasks include backend = "external-cli" or "opencode".
  • Task status/result formatting shows external-cli outputs.
  • Config/schema updates (Zod + JSON schema) and provider factory.
  • Unit tests for provider factory, types, and manager; existing tests remain passing.

• Migration

  • Enable in config: external_cli.enabled=true, provider="cursor", default_model, optional models/workspace/timeout.
  • Requirements: Cursor installed and authenticated; verify with cursor-agent -p --model <model> --output-format json "test".
  • No changes needed when disabled (default).

^{Written for commit d83e221. Summary will update on new commits.}

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[antoniomdk]

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